Is Climate Change Increasing Tornadoes?

With the tragic Moore, Oklahoma tornado one of the largest in history—if not the largest—it's easy to wonder if there's a connection to climate change, especially as we've just passed all-time record levels of carbon dioxide in the atmosphere. But the answer isn't so clear. While climate change is linked to a huge range of effects, from heat waves and drought to floods and hurricanes, there's much less known about tornadoes.

Part of the problem: there aren't good records of tornadoes over time, so it's hard to see how things are changing. Tornadoes are naturally variable—some years a region will see a lot, some years none. And it's also hard to predict how they will react to changing global temperatures, because those changes affect two causes of tornadoes in completely opposite ways. A writer from ClimateNexus explains on Mother Nature Network:

Tornadoes, violently rotating columns of air spawned by thunderstorms, occur when available energy—warm, moist air at low levels and cold, drier air above—meets vertical wind shear, which provides the source of the rotation. Climate change enhances the former, also known as "convective available potential energy,'' or CAPE, and diminishes the latter.

So as the planet warms, in theory, it might make tornadoes both more and less likely at the same time. As one of the scientists says in the MNN article, "With tornadoes, what we don't know is as much as we do know."